A superb reference, though somewhat dated. Gives lots of plant uses as well as information on plant habit and habitat. The entire flora (13 volumes) can now be downloaded from http://www.archive.org/

]. The stems sometimes become softly woody.
The plant is sometimes harvested from the wild for its edible leaves, which are used locally. The plant is also cultivated in tropical W Africa, Cuba and SE Asia as a vegetable, in Thailand for its medicinal uses and in various parts of the tropics as an ornamental[